Segment information - Information about revenue, profit and assets (Details)	12 Months Ended
	Dec. 31, 2016 USD ($) item	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Segment information
Number of reportable segments | item	2
Cost of sales included in processing and services costs	$ 12,701,351	$ 14,860,804	$ 13,483,282
Long-lived assets	$ 7,000,000	7,400,000
Number of geographical regions in which the entity conducts its business | item	3
Net Revenue:
Net revenue	$ 54,337,407	52,815,088	47,368,739
Gross Profit:
Total gross profit	31,186,050	27,050,624	23,481,778
Income from operations before benefit (provision) for income taxes:
Total gross profit	31,186,050	27,050,624	23,481,778
Selling, general and administrative expenses	20,860,469	20,408,308	18,370,691
Restructuring charges	504,141	283,726	1,227,204
Income from operations	9,821,440	6,358,590	3,883,883
Interest expense	(273,873)	(57,575)	(65,122)
Interest income	1,763	1,579	2,212
Other income	93,016	89,494	139,875
Total other (expense) income, net	(179,094)	33,498	76,965
Income from operations before benefit (provision) for income taxes	9,642,346	6,392,088	3,960,848
Operating segments
Net Revenue:
Net revenue	41,627,875	38,189,095	34,919,585
Corporate allocated cost of sales
Net Revenue:
Net revenue	10,441,825	11,138,471	11,437,807
Multi-currency processing services
Segment information
Cost of sales included in processing and services costs	2,300,000	3,700,000	2,000,000
Net Revenue:
Net revenue	34,087,963	33,463,439	30,954,085
Gross Profit:
Total gross profit	31,828,437	29,741,106	28,908,610
Income from operations before benefit (provision) for income taxes:
Total gross profit	31,828,437	29,741,106	28,908,610
Payment processing services
Net Revenue:
Net revenue	20,249,444	19,351,649	16,414,654
Gross Profit:
Total gross profit	9,799,438	8,447,989	6,010,975
Income from operations before benefit (provision) for income taxes:
Total gross profit	9,799,438	8,447,989	6,010,975
APAC | Multi-currency processing services
Net Revenue:
Net revenue	16,196,244	16,265,076	16,621,147
Gross Profit:
Total gross profit	16,095,147	16,136,562	16,513,492
Income from operations before benefit (provision) for income taxes:
Total gross profit	16,095,147	16,136,562	16,513,492
Americas | Multi-currency processing services
Net Revenue:
Net revenue	10,180,218	7,162,346	6,893,337
Gross Profit:
Total gross profit	9,515,560	6,725,223	6,733,037
Income from operations before benefit (provision) for income taxes:
Total gross profit	9,515,560	6,725,223	6,733,037
EMEA | Multi-currency processing services
Net Revenue:
Net revenue	7,711,501	10,036,017	7,439,601
Gross Profit:
Total gross profit	6,217,730	6,879,321	5,662,081
Income from operations before benefit (provision) for income taxes:
Total gross profit	$ 6,217,730	$ 6,879,321	$ 5,662,081